1. Field of Invention
The present invention relates to apparatus for the inspection and maintenance of nuclear steam generator equipment. The invention has particular application to the inspection and maintenance of pipes or other tubular passages, such as the primary loop conduit of a nuclear steam generator.
2. Description of the Prior Art
Direct on-site inspection of nuclear steam generating facilities by inspection personnel is limited because of the danger of man-rem exposure. Thus, the use of remotely-controlled mechanical inspection apparatus is necessary. A number of different types of self-propelled pipe crawler vehicles have been provided in the prior art for traversing the interior of pipes or other tubular conduits for inspection or maintenance purposes, most of these devices having been provided for use by pipeline companies. Some of these vehicles are intended for carrying of operating or inspection personnel, but others are remotely-controlled.
However, the prior pipe crawler vehicles which are intended for use in large-diameter pipes, are designed for use where there is direct access to one end of the pipe. They are not capable of passing through openings having a diameter substantially less than the diameter of the pipe. Thus, such vehicles would not be suitable for use in a nuclear steam vessel, wherein the only access to the primary loop conduit is through a much smaller-diameter manway. Furthermore, such prior devices are generally quite heavy and cumbersome and cannot be handled by one person.
A pipe crawling vehicle has been provided specifically for use in nuclear steam generator vessels, such a device being illustrated in U.S. Pat. No. 4,244,296. But that device is rather complex, including a plurality of pivotally movable arms, each independently driven, necessitating a plurality of drive mechanisms. Furthermore, the vehicle is quite heavy and cumbersome, necessitating the use of a special loading apparatus for hoisting the device into the nuclear steam generator vessel. Finally, the vehicle is of limited utility. It has only two support wheels, mounted fore and aft and, therefore, the pivoting arms must be utilized to maintain the stability of the vehicle in the tube. Accordingly, the device is usable only in a pipe or other confined space wherein there is a surface for the arms to bear against.